1. Field
The present invention relates to a folding unit for corrugated cardboard sheets in inline production of corrugated cardboard boxes, comprising a pair of parallel and laterally displaceable folding beams each with an endless conveying belt, which folding beams extend from the inlet of the folding unit to the outlet of the folding unit, a pair of folding rules which are arranged under the respective folding beams and which extend from the inlet of the folding unit and towards, but not all the way to, the outlet of the folding unit, a pair of folding rods fixedly positioned outside the respective folding rules and at angle to the respective folding rules, said folding rods being arranged in the folding unit front portion, seen in the conveying direction of the corrugated cardboard sheets, a pair of folding belts which are arranged under and cooperate with a respective folding rule and extend from an associated guide roller with a vertical shaft at the terminal end of the folding rods in the conveying direction to an associated guide roller with a horizontal shaft substantially adjacent to the outlet, and a pair of wheel stands which are each engaged with the respective folding belts in a position in the conveying direction of the corrugated cardboard sheets after the terminal end of the folding rules and substantially adjacent to the respective folding beams, whereby a corrugated cardboard sheet supplied at the inlet of the folding unit is grasped by the pair of conveying belts and conveyed along the folding rules and the two outermost panels of the corrugated cardboard sheet being successively folded from 0° to 90° by the respective folding rods in cooperation with the associated folding rule, after which each panel folded 90° is engaged with the associated folding belt and the folding rule cooperating with said folding belt for continued folding and then leaves the associated folding rule to be contacted with the associated wheel stand and is finally delivered from the pair of guide rollers with a horizontal shaft, the panels folded 180°, at the outlet.
The invention also relates to a method of folding corrugated cardboard sheets in inline production of corrugated cardboard boxes, comprising the steps of intermittently feeding corrugated cardboard sheets into a folding unit during application of glue; in the folding unit first portion, seen in the conveying direction of the corrugated cardboard sheet, successively folding the two outermost panels of the corrugated cardboard sheet from 0° to 90° by means of a pair of folding rules and a pair of folding rods cooperating with the same; in the folding unit second portion, seen in the conveying direction of the corrugated cardboard sheet, successively folding the two outermost panels of the corrugated cardboard sheet from 90° to 180° by means of a pair of folding belts and said pair of folding rules as well as a pair of wheel stands, by means of which the angle of each folding belt to the horizontal plane is set, and by means of a guide rod guiding the folded corrugated cardboard sheet between a pair of rolls for gluing the glue flap of one folded panel to the other folded panel.
2. Description of the Related Art
Modern production of corrugated cardboard boxes takes place in what is referred to as inline machines. These machines are characterised in that all operations occur in line in one and the same machine. Corrugated cardboard sheets or blanks, which are adjusted to the format of the intended boxes, are intermittently fed one by one by means of a feeding unit in the inline machine.
After that the sheets are printed in one or more printing units which are located after the feeding unit. Then follow scoring, slitting and cutting of the glue flap which take place in the slitting unit of the machine. The next operation is optional punching of air holes, handle holes or any other punching depending on the construction of the boxes. This takes place in what is referred to as the punching unit. The folding unit is positioned after the punching unit. In the folding unit, glue is applied to the glue flap of the sheet, after which 180° folding of the outer panels of the sheet takes place. The glue flap is glued to the outer part of the panel on the opposite side of the sheet.